This invention relates to a liquid separator for separating upper and lower liquid layers from each other stored in a flexible container. More particularly, it relates to a liquid separator for separating various blood portions or components such as blood plasma, red cells, etc. from blood stored in a flexible container such as a blood bag or the like.
In recent years, component transfusion in which only a blood component required by a patient is transfused to the patient has been employed instead of whole blood transfusion. On the other hand, blood plasma is collected for producing plasma preparations.
A blood bag system so-called "multibag" in which bags are connected to each other by tubes is used for blood component transfusion or preparing blood preparations. In such a blood bag system, blood stored in a blood collection bag (main bag) is separated into plasma component layer at the upper layer and blood cell component layer at the lower layer by centrifugation. The separated plasma component should be taken out without mixing with the blood cell component.
For this purpose, there are known liquid separators, for example, disclosed in Japanese Patent Publication Nos. Sho 57-30507 and Sho 63-47471.
As shown in FIG. 9, the liquid separator 80 disclosed in the Japanese Patent Publication No. Sho 57-30507 comprises a box base 81, a wall plate 82 perpendicularly mounted on the box base 81, a separator plate 83 pivotally supported on the box base 81 and movable toward the wall plate 82, a lever 84 for pushing the separator plate 83, and a hook 85 for the lever 84. The wall plate 82 is provided with a hanger 86 for hanging a blood bag. A blood bag after centrifugation is hung by the hanger 86 of the wall plate 82 and the lever 84 is then moved upward to sandwich the blood bag between the separator plate 83 and the wall plate 82. The blood bag is pressed by the separator plate 83 and the wall plate 82 so that plasma component of the upper layer of blood in the blood bag is discharged through a tube connected to the blood bag.
As shown in FIG. 10, the liquid separator 90 disclosed in the Japanese Patent Publication No. Sho 63-47471 comprises a side wall 91 of a box case 2, connecting rods 94 and 95 and a pressing plate 93 arranged parallelly with the side wall 91. The pressing plate 93 can be moved toward the side wall 91 by the connecting rods 94 and 95. A blood bag 96 after centrifugation is sandwiched between the side wall 91 and the pressing plate 93 and pressed by the pressing plate 93 so that blood in the blood bag 96 is discharged.
Plasma component separated from blood cell component in a blood bag should be taken out from the blood bag without mixing with the blood cell component and with good efficiency.
In the liquid separator 80 disclosed in the Japanese Patent Publication No. Sho 57-30507, the blood bag is pressed by manipulating the lever 84. However, a delicate manipulation of the lever 84 is required in order not to disturb the boundary between the plasma component and the blood cell component in the blood bag. Such a delicate manipulation was hard.
In the liquid separator 90 disclosed in the Japanese Patent Publication No. Sho 63-47471, the blood bag 96 is automatically pressed. The pressure for the blood bag 96 is fixed or increased at the end of the pressurization. In this liquid separator 90, however, there is the high possibility that the boundary between the plasma component and the blood cell component in the blood bag is disturbed and both are mixed with each other. Mixing of the components obstructs the accurate operation of a sensor for detecting the boundary between the components.